Re: ERR_BELOW_1MB tests signed address?

[Jochen Hoenicke]

On May 31, Mike Tsao wrote:
> I built an ELF executable with a load address of 0xC0000000.
> 
> GRUB had some trouble with it, complaining that "Loading below 1MB is not
> supported." The commands I used to load it were root (hd0,0); makeactive;
> kernel mydir/myfile (Bochs for Win32, FAT file system).
> 
> Changing the load address to 0x00200000 solved the problem.
> 
> I think this is the GRUB code that gave the error (5.96.1, stage2/boot.c,
> lines 110-111):
> 
> if (((int) entry_addr) < 0x100000)
>     errnum = ERR_BELOW_1MB;
> 
> Is this a bug? 

Yes and the CVS version has fixed it:

      if (entry_addr < (entry_func) 0x100000)
        errnum = ERR_BELOW_1MB;


But AFAIK a load address of 0xc0000000 still won't work, except if you
have more than 3GB of RAM.  This is because the multistandard
explicitly says that there is no paging, so virtual and physical
addresses are identical.

  Jochen